The present invention concerns printing and display of drawings within a computing system and pertains particularly to the preview of drawings before printing.
While of general use in the printing and display field, the present invention is especially useful to the field of computer driven printers particularly designed for producing engineering or other large drawings on paper, vellum, film or other print media which is drawn through the mechanism from a roll or from a manual or automatic sheet feed media path. Typically, the media may have a width from 81/2 inches to as much as 3 or 4 feet or more.
With reference to a rectangular coordinate system, the paper or other print media is drawn through the printer in the X direction and a thermal inkjet printer carriage is mounted for movement transversely of the paper in what shall be referred to as the Y direction. A sheet of paper or other print media is either manually fed or paper is drawn from a supply roll thereof around a platen roller which may or may not be power driven. When the printer apparatus employs a thermal inkjet printing head or heads, precise control of the spacing between the print heads and the surface of the print media on which printing is to take place is essential otherwise acceptable print resolution is lost.
Inkjet printers, such as those sold by Hewlett Packard Company, offer substantial improvements in speed over the conventional X-Y plotter. Inkjet printers typically include a pen having an array of nozzles. The pens are mounted on a carriage which is moved across the page in successive swaths. Each inkjet pen has heater circuits which, when activated, cause ink to be ejected from associated nozzles. As the pen is positioned over a given location, a jet of ink is ejected from the nozzle to provide a pixel of ink at a desired location. The mosaic of pixels thus created provides a desired composite image.
Using printers for large print media introduces special problems in printer software. For example, many operating systems, such as the Microsoft Windows operating system, available from Microsoft Corporation having a business address of One Microsoft Way, Redmond, Wash. 98052, are currently limited as to the size of papers supported. This limitation has been inherited by applications as either a limited paper size support or as system crashes with big paper sizes.
One of the most used approaches to overcome size limitations of paper sizes is to scale a drawing. The scaling is done by the printer driver internally or in conjunction with a graphic-device interface (GDI) within the Windows operating system. Scaling is often presented as one scale factor or a source and destination paper size.
Traditional implementations of scaling in applications and drivers achieve their results by multiplying or dividing the received coordinates by a scale factor. Some scaling procedures accept only integer scale factors to avoid rounding problems.
Another way to overcome the size limitations of paper sizes is to report a bigger resolution than the device resolution. In that way the application and the GDI are forced to generate more pixels. However, big scale factors resulting in higher resolutions increase the likelihood that an application will cause the operating system to crash. In addition, there is limit to the amount of pixels which can be handled by the GDI.
Another problem which arises when using printers for large-sized print media, and sometimes even arises when using printers for normal-sized print media, is the lack of an adequate print preview. A print preview feature is particularly important for large-sized media printers because the cost of print media and ink can be significant, and reprinting can be costly both in the cost of print media and ink as well as in time spent printing.
Some applications, allow a print preview. However, very often the application print preview feature shows only a very inadequate preview of the drawing to be printed. For example, the application print preview may only show a representation of physical paper and an area within the physical paper on which the printing will take place. Alternatively, the application print preview may show a correct representation of the physical paper without showing if the drawing is going to be clipped because it will be outside of the plotting area.